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STATE  OF  ILLINOIS 
DEPARTMENT  OF  REGISTRATION  AND  EDUCATION 

DIVISION  OF  THE 

STATE  GEOLOGICAL  SURVEY 

FRANK  W.  DE  WOLF.  Chief 


Cooperative  Mining  Series 

BULLETIN  22 


WATER-GAS  MANUFACTURE  WITH 
CENTRAL  DISTRICT  BITUMINOUS  COALS 
AS  GENERATOR  FUEL  \i\ 


BY 
W.  W.  ODELL,  U.  S.  Bureau  of  Mines, 

and 
W.  A.  DtJNKLEY,  State  Geological  Survey  Division. 


ILLINOIS  MINING  INVESTIGATIONS 

Prepared  under  a  cooperative  agreement  between  the  Illinois  State  Geological  Survey 

Division,  the  Engineering  Experiment  Station  of  the  University  of  Illinois, 

and  the  U.  S.  Bureau  of  Mines. 


PRINTED  BY  AUTHORITY  OF  THE  STATE  OF  ILLINOIS 


URBANA,  ILLINOIS 

1918 


ILLINOIS  MINING  INVESTIGATIONS 

Cooperative  Agreement 
GAS  SECTION 

The  difficulty,  due  to  war  conditions,  of  obtaining  adequate  and 
reliable  delivery  of  eastern  gas-coal  and  of  coke  has  suggested  the 
wider  use  in  gas  manufacture  of  low-sulphur  coal  mined  in  the  central 
district,  comprising  Illinois,  Indiana,  and  western  Kentucky. 

The  needs  of  the  gas  industry,  and  the  desire  of  the  U.  S.  Fuel 
Administration  to  meet  those  needs,  has  led  to  the  appointment  by 
Governor  Frank  O.  Lowden,  of  a  Technical  Committee  on  Gas,  By- 
products, and  Public  Utilities,  to  act  in  an  advisory  relation.  The 
committee  includes  representatives  of  the  Illinois  Gas  Association,  the 
,U.  S.  Bureau  of  Mines,  the  Engineering  Experiment  Station  of  the 
University  of  Illinois,  and  the  State  Geological  Survey  Division  of 
the  Department  of  Registration  and  Education,  State  of  Illinois. 

Previously,  some  studies  of  the  use  of  Illinois  coal  in  retort-gas 
manufacture  and  in  by-product  coke  ovens,  and  of  the  chemical  and 
physical  properties  of  Illinois  coal,  have  been  conducted  under  the  Illi- 
nois Mining  Investigations,  cooperative  agreement, — a  joint  agency 
of  the  U.  S.  Bureau  of  Mines,  the  University  of  Illinois,  and  the 
State  Geological  Survey  Division.  The  continuation  and  expansion 
of  this  work  has  been  recommended  by  the  Technical  Committee  and 
the  Fuel  Administration.  In  response  a  Gas  Section  has  been  created, 
and  experienced  gas  engineers,  chemists,  and  other  specialists  have 
undertaken  a  program  of  experiment  on  a  commercial  scale  to  extend 
the  use  of  central  district  coal  in  water-gas  generators  and  in  gas 
retorts. 

The  results  of  the  investigations  will  be  published,  and,  in  addi- 
tion, the  operators  of  gas  plants  in  the  region  naturally  tributary  to 
central  district  coal  will  be  advised  by  the  Technical  Committee,  of 
the  progress  from  time  to  time,  and  will  be  urged  to  witness  and  par- 
ticipate in  the  tests  and  to  introduce  in  their  own  plants  new  or  im- 
proved practices  which  will  lessen  the  burden  on  the  railroads,  and 
assist  the  mines  and  the  coke  ovens  to  meet  the  unprecedented  demands 
due  to  the  war. 

Inquiries  and  suggestions  regarding  the  gas  experiments  should 
be  addressed  to  Gas  Section,  Room  305  Ceramics  Bldg.,  Urbana,  Illi- 
nois. 


3  3051  00006  4042 


STATE  OF  ILLINOIS 
DEPARTMENT  OF  REGISTRATION  AND  EDUCATION 

DIVISION  OF  THE 

STATE  GEOLOGICAL  SURVEY 

FRANK  W.  DE  WOLF,  Cbief 


Cooperative  Mining  Series 

BULLETIN  22 


WATER-GAS  MANUFACTURE  WITH 

CENTRAL  DISTRICT  BITUMINOUS  COALS 

AS  GENERATOR  FUEL 


BY 
W.  W.  ODELL,  U.  S.  Bureau  of  Mines, 

and 
W.  A.  DUNKLEY,  State  Geological  Survey  Division. 


ILLINOIS  MININO  INVESTIGATIONS 

Prepared  under  a  cooperative  agreement  between  the  Illinois  State   Geological   Survey 

Division,  the  Engineering  Experiment  Station  of  the  University  of  Illinois, 

and  the  U.  S.  Bureau  of  Mines. 


PRINTED  BY  AUTHORITY  OF  THE  STATE  OF  ILLINOIS 


URBANA,  ILLINOIS 
1J)18 


STATE  OF  ILLINOIS 
DEPARTMENT  OF  REGISTRATION  AND  EDUCATION 

DIVISION  OF  THE 

STATE  GEOLOGICAL  SURVEY 

Frank  W.  DeWolf,  Chief 


Committee  of  the  Board  of  Natural  Resources 
and  Conservation 

Francis  W.  Shepardson,  Chairman 

Director   of   Registration   and   Education 

David  Kinley 

Representing  the   President  of  the  Uni- 
versity of  Illinois 

Thomas  C.  Chamberlin 
Geologist 


CONTENTS 


PAGE 

Introduction    7 

Objections  offered  to  the  use  of  bituminous  coal  as  generator  fuel.  . .  10 

Methods  of  overcoming  objections 11 

Water-gas  manufacture  at  plants  using  bituminous  coal  fuel 13 

Kind  and  size  of  fuel 14 

Depth  of  fuel  bed  and  its  relation  to  blast  and  steam  cycle 14 

Quality  and  quantity  of  oil  used 15 

Distribution  of  oil  in  the  carburetor 16 

Purging  the  machine   with  air 16 

Operating  data  from  typical  plants  where  coal  is  used  as  generator 

fuel    16 

Discussion  of  table 19 

The  economical  advantage  of  central  district  coal  as  a  water-gas  gen- 
erator   fuel 20 

Cost  of  materials 21 

Cost  of  operating  labor 22 

Cost  of  repairs 22 

Overhead  and  miscellaneous  expense 22 

Income  from  sale  of  residuals 23 

Summary   '. 23 

Conclusions    24 

Suggested  problems  for  further  study 24 


Digitized  by  the  Internet  Archive 

in  2012  with  funding  from 

University  of  Illinois  Urbana-Champaign 


http://archive.org/details/watergasmanufact22odel 


ILLUSTRATIONS 


FIGURE  PAGE 

1.  Bituminous  coal  zone  C    6 

2.  Bituminous  coal  zone  D    8 

3.  Bituminous  coal  zone  E    9 


TABLES 


1.  Practice  at  four  water-gas  plants 18 

2.  A  comparison  of  the  approximate  manufacturing  costs  of  water-gas 

with  coke  and  with  coal  as  generator  fuel 23 


Fig.  1. — Bituminous  coal  zone  C,  established  by  the  U.  S.  Fuel  and  the  U.  S.  Rail- 
road Administrations,  April  1,  1918,  and  corrected  to  October  1,  1918.  Includes  low-sulphur 
coal  areas  in  southern   Illinois. 

At  the  time  this  map  was  made,  producing  districts  in  Illinois  were  restricted  in 
their  shipments  of  coal  during  the  winter  to  markets  within  and  along  the  solid  boundary 
line,  and  during  the  summer  to  markets  within  and  along  the  heavy  dashed  boundary  line 
and  its  solid  continuation  south  from  Albia,  Iowa,  and  Milwaukee,  Wisconsin.  Under  date 
September  26,   1918,  this  order  was  modified  as  follows: 

The  Lower  Peninsula  of  Michigan  is  to  be  included  for  the  winter  in  Zone  C.  Those 
parts  of  Wisconsin  and  Minnesota  lying  between  the  solid  and  dashed  lines  in  the  figure  may 
receive  coal  the  entire  year  from  Illinois. 

The  period  during  which  shipments  may  be  made  into  South  Dakota  is  extended  to 
November  1. 


WATER-GAS  MANUFACTURE  WITH 

CENTRAL  DISTRICT  BITUMINOUS 

COALS  AS  GENERATOR  FUEL 

By  W.  W.  Odell,  U.  S.  Bureau  of  Mines,  and 
W.  A.  Dunkley,  State  Geological  Survey  Division 


INTRODUCTION 

This  circular  presents  data  on  present  water-gas  manufacture, 
as  gathered  by  the  writers  during  an  inspection  of  twenty  water-gas 
plants  in  Illinois  and  surrounding  states,  in  which  bituminous  coal  from 
the  central  mining  district  of  Illinois,  Indiana,  and  western  Kentucky 
is  being  used  in  place  of  coke  as  a  generator  fuel.  The  term  "central 
district  bituminous  coals"  as  used  in  this  paper  refers  to  those  origin- 
ating in  this  district. 

The  generator  fuel  formerly  used  in  these  plants  was  either  retort  - 
house  coke  made  usually  from  an  eastern  coal,  or  else  oven  coke  trans- 
ported from  a  distance.  Eastern  coal  produces  a  better  coke  in  the 
gas  retort  than  western  coal,  and  therefore  a  coke  that  can  be  used 
to  greater  advantage  in  the  water-gas  set.  This  coke  and  the  coke 
hauled  direct  from  the  east  will  give  a  greater  production  of  gas  from 
a  water-gas  set  in  a  given  time  than  will  uncoked  bituminous  coal  from 
either  the  east  or  the  central  district.  I  low  ever,  the  well-known  con- 
ditions prevailing  at  the  present  time  in  the  coal  and  railroad  industries 
make  it  desirable  and  perhaps  necessary  to  haul  as  little  coal  or  coke 
as  possible  from  the  eastern  points  of  production  to  the  central  west. 
The  use  of  central  district  bituminous  coals  as  generator  fuel  will  not 


During  the  entire  year  producing  districts  of  Vermilion  County,  Illinois,  along  the 
Wahash  Railway  may  in  addition  ship  coal  to  points  of  delivery  along  the  Wabash  Railway 
within  Indiana.  Similarly,  producing  districts  of  Sangamon  County  may  ship  to  stations 
along  the  Cincinnati,  Indianapolis,  and  Western  Railroad,  as  far  east  as  Indianapolis,  and 
including  points  of  delivery  within  switching  limits  on  connecting  lines.  Neither  of  these 
counties  produces  low-sulphur  coal,  however. 

A  modification  affecting  the  distribution  of  Jackson  and  Randolph  county  coals  is  as 
follows:  All  producers  located  along  the  Mobile  and  Ohio  Railroad  and  short-line  connec- 
tions in  Illinois  may  ship  coa!  to  points  of  delivery  on  the  Mobile  and  Ohio  Railroad  within 
Tennessee  and  Mississippi,  as  far  south  as  Meridian,  Mississippi,  including  stations  within 
switching  limits  on  connecting  railway  lines.  Jackson  County  is  a  producer  of  low-sulphur 
coal    from   seam    No.   2. 

Consult  the  District  Representative  of  the  Fuel  Administration,  2017  Fisher  Building, 
Chicago,  to  learn  decisions  on  suggested  changes  still  pending.  <  >i  these  changes,  the  one 
affecting  particularly  the  coal-gas  industrj  relates  to  the  addition  of  a  pari  of  Iowa  to  the 
territory   of  Zone  C. 


WATER-GAS    MANUFACTURE 


only  reduce  freight  traffic  but  will  release  for  other  necessary  uses 
coke  now  used  as  water-gas  fuel.  Furthermore,  such  successful  prac- 
tice with  these  coals  may  be  developed  that  a  new  permanent  market 
for  them  will  be  established.  For  these  reasons,  it  is  desirable  that 
central  district  coals  be  substituted  for  eastern  coal  and  coke  wherever 
possible. 


Fig.  2. — Bituminous  coal  zone  D,  established  by  the  U.  S.  Fuel  and  the  U.  S.  Rail- 
road Administrations,  April  1,  1918,  and  corrected  to  October  1,  1918.  Includes  low-sulphur 
coal  in  western  Indiana. 

As  the  zoning  was  originally  established,  all  producing  districts  of  Indiana  were  re- 
stricted in  their  shipments  of  coal  to  markets  within  and  along  the  heavy  boundary  line. 
Under  date  September  26,  this  order  was  modified  so  as  to  include  all  of  the  Lower  Penin- 
sula of  Michigan  in  the  territory  of  Zone  D. 

Last  winter  the  shortage  of  coke  fuel  at  many  water-gas  plants 
led  to  some  independent  experimentation  with  bituminous  coal  of  vari- 
ous sizes  from  districts  in  Illinois  and  Indiana  where  low-sulphur  coal 
is  mined.  As  a  rule  the  results  have  been  encouraging.  The  plants 
have  been  kept  going,  and  under  certain  conditions  central  district  coal 
as  generator  fuel  has  proven  more  economical  than  coke. 

This  report  outlines  the  difficulties  which  were  anticipated,  and 
those  actually  met  and  overcome  in  connection  with  the  change  of 
fuel ;  and  presents  operating  data  from  several  plants  at  which  central 


INTRODUCTION 


district  coal  is  used  successfully.  Actual  operating  costs  listed  reveal 
no  increase  due  to  the  use  of  bituminous  coal ;  in  fact  an  actual  saving 
is  indicated  where  the  capacity  of  the  plant  is  ample. 


Houst 


Fig.  3. — Bituminous  coal  zone  E,  established  by  the  U.  S.  Fuel  and  the  U.  S.  Rail- 
road Administrations,  April  1,  1918,  and  corrected  to  July  1,  1918.  Includes  low-sulphur 
coal  in  western  Kentucky. 

Producing  districts  in  western  Kentucky,  shown  in  hlack,  are  restricted  in  their  ship- 
ments of  coal  to  markets  within  or  along  the  heavy  houndary  line. 

Modifications  of  the  original  zoning  made  prior  to  July  1,  1918,  have  been  incorporated 
in   the   map.      Later   modifications  affecting   the   gas-coal   markets   are   as    follows: 

Producers  in  the  western  Kentucky  districts  may  in  addition  distribute  their  coal  (1) 
along  the  Louisville,  Cincinnati  and  Lexington  Division  of  the  Louisville  and  Nashville 
Railway  between  Louisville  and  Newport,  Kentucky,  inclusive,  and  (2)  in  Cincinnati,  Ohio, 
and   points   of  delivery   located   within   the    Cincinnati   switching   district. 

Producers  of  this  district  may  not  ship  coal  without  permit  into  those  parts  of  Illi- 
nois, Wisconsin,  and  Indiana,  included  originally  in  zone  E  as  shown  by  the  heavy  boundary 
line.  A  provision  is  made,  however,  which  should  he  noted  by  the  coal-gas  manufacturer: 
Any  western  Kentucky  producer  may  ship  coal  of  special  quality  for  special  uses  to  points 
of  delivery  within  the  prohibited  territory  under  permit  which  may  be  obtained  from  the 
Fuel   Administration   on   application   of  the  consumer. 


10  WATER-GAS    MANUFACTURE 

The  inspection  reveals  that  there  are  still  many  operating  prob- 
lems to  be  solved ;  and  that  a  further  study  of  these  will  be  of  benefit 
to  the  gas  industry.  Consequently,  this  circular  is  only  preliminary  to 
the  publication  of  the  results  of  further  investigations  which  are  being 
undertaken  by  the  cooperating  agencies. 

OBJECTIONS  OFFERED  TO  THE  USE  OF  BITUMINOUS 
COAL  AS  GENERATOR  FUEL 

At  some  plants  operators  have  been  deterred  from  using  bitum- 
inous coal  as  generator  fuel  because  of  difficulties  expected  on  the 
basis  of  their  experience  with  coke  fuel.  It  is  usually  anticipated  that 
the  coking  or  matting  together  of  the  fresh  coal  in  the  generator  will 
obstruct  the  passage  of  blast  and  steam  through  the  fire,  thereby  lead- 
ing to  the  formation  of  flues  through  the  fuel  bed  with  consequent 
decreased  capacity  and  efficiency  of  the  generating  set.  The  large 
amount  of  volatile  matter  which  is  released  when  fresh  coal  is  charged 
into  the  generator  is  another  anticipated  cause  of  difficulty.  Not  only 
is  the  fear  of  creating  a  smoke  nuisance  a  deterrent  with  some  oper- 
ators whose  plants  are  located  where  complaints  would  likely  arise, 
but  the  ill  effect  of  this  large  amount  of  volatile  matter  upon  the  oper- 
ation of  the  plant  is  feared.  It  is  often  anticipated  that  if  an  effort 
is  made  to  burn  all  of  this  volatile  matter  in  the  machine  or  at  the 
stack,  these  parts  of  the  apparatus  will  be  seriously  overheated,  result- 
ing not  only  in  upsetting  the  operating  balance  but  also,  perhaps,  in 
injury  to  the  machine  itself.  Some  operators  also  anticipate  that  the 
operation  of  the  hot  valves  will  be  impeded  by  the  tar  present  in  the 
gases  given  off  by  the  generator  and  that  the  checker  bricks  in  the  car- 
buretor and  superheater  will  be  fouled  rapidly ;  also  that  the  purifying' 
equipment  of  the  plant  will  be  overloaded  by  excessive  sulphur  in  the 
gas.  On  account  of  the  relatively  low  melting  point  of  the  ash  from 
most  central  district  coals,  as  shown  when  cokes  from  these  coals  are 
used  as  generator  fuel,  the  formation  of  excessive .  and  troublesome 
clinker  has  also  been  expected  from  the  use  of  these  coals. 

In  general,  these  difficulties  have  been  met  and  overcome.  It  is 
true  that  the  average  figures  at  the  twenty  plants  visited  showed  a 
decreased  capacity  of  the  set  of  about  25  per  cent  when  using  coal  in 
place  of  coke,  and  an  increase  of  about  30  per  cent  in  the  amount  of 
fuel  needed  for  making  1,000  cubic  feet  of  gas.  However,  the  cost 
of  coal  being  less  than  coke,  and  the  amount  of  oil  necessary  being 
decreased  about  10  per  cent,  the  actual  cost  of  gas  per  1,000  cubic  feet 
decreased  wdien  coal  was  used. 


OBJECTIONS    TO   BITUMINOUS    COAL  11 

METHODS  OF  OVERCOMING  OBJECTIONS 

When  the  central  district  coals  are  charged  into  a  water-gas  gen- 
erator in  the  same  volume  as  coke  would  be  charged,  a  rather  dense 
firm  mat  of  coke  is  formed  on  blasting.  The  mat  arches  over  the  top 
and  does  not  drop  without  being  poked  from  the  charging  door.  This 
property  of  matting  when  heavy  charges  are  used,  naturally  increases 
the  tendency  to  form  flues  or  chimneys  in  the  fuel,  and  reduces  the 
capacity  and  operating  efficiency  of  the  machine.  To  overcome  this 
caking  difficulty,  coal  must  be  charged  into  the  generator  in  much 
smaller  quantities  by  volume  than  coke,  since  coal  is  heavier  per  unit 
of  volume.  Some  operators,  particularly  those  handling  the  larger  sets, 
carry  a  deeper  fuel  bed  than  they  would  otherwise  consider  possible, 
by  making  "split"  steam  runs  ;  that  is,  they  reverse  the  direction  of 
flow  of  steam  through  the  fire  while  the  run  is  in  progress. 

At  a  few  plants  some  trouble  has  been  experienced  from  smoke, 
especially  where  the  plant  is  located  in  a  residence  district.  Any  smoke 
in  these  districts  results  in  immediate  complaint.  It  is  very  difficult 
to  avoid  smoke  or  oil  fumes  at  all  times  even  with  coke  fuel.  With 
coal  the  trouble  is  increased  because  it  is  especially  difficult  to  com- 
pletely burn  the  hydrocarbons  given  off  from  the  incomplete  combus- 
tion of  coal  in  the  machine  during  the  early  stages  of  the  heating-up 
period  when  the  checker  bricks  in  the  carburetor  are  not  hot  enough 
to  ignite  these  gases.  Where  a  set  is  operated  to  almost  its  full  capacity, 
these  bricks  will  not  usually  cool  off  so  much  during  lay-over  periods 
that  any  great  difficulty  will  be  experienced  in  quickly  igniting  the 
generator  gases,  but  in  a  plant  operating  but  a  few  hours  a  day  the 
problem  is  greater.  One  ingenious  operator  has  hastened  the  ignition 
by  means  of  an  automobile  spark  plug  screwed  into  a  short  length 
of  pipe  extending  above  the  carburetor.  With  this  device  he  is  able 
to  ignite  the  gases  passing  into  the  carburetor  long  before  the  bricks 
would  become  hot  enough  to  ignite  them.  At  the  same  time  the  heat- 
ing up  of  the  carburetor  and  superheater  is  hastened.  In  order  to 
reduce  the  smoke  formed  after  coaling  the  machine,  some  operators 
blast  before  coaling  and  make  a  steam  run  before  blasting  again. 

The  prevention  of  the  overheating  of  carburetor  and  superheater 
during  the  blasting  period  lies  in  the  proper  timing  of  this  operation. 
It  is  generally  accepted  that  on  blasting  coal  containing  a  high  per- 
centage of  volatile  matter  a  gas  will  be  produced  containing  some  of 
the  hydrocarbons  of  the  volatile  matter  of  the  coal.  Such  blast  gases 
are  higher  in  heating  value  than  the  blast  gases  from  coke,  and  when 
burned  in  the  machine  they  produce  more  heat  in  the  carburetor  and 


12  WATER-GAS    MANUFACTURE 

superheater.  Therefore,  a  long  blast  on  such  a  fuel  as  central  dis- 
trict bituminous  coal  will  result  in  the  production  of  more  heat  than 
is  required  for  cracking  and  fixing  the  carburetting  oil.  This  means 
that  the  gas  in  excess  of  the  amount  required  for  the  proper  heating 
of  the  checker  brick  has  to  be  burned  at  the  stack.  Not  only  is  this 
a  wasteful  process,  but  it  so  heats  the  stack  that  there  is  danger  of 
melting  it.  Therefore  prolonged  blasting  such  as  is  sometimes  prac- 
ticed with  coke,  is  undesirable  when  bituminous  coal  is  used  as  a  gen- 
erator fuel. 

More  tar  is  formed  with  coal  as  generator  fuel  than  with  coke, 
the  average  increase  noted  being  25  per  cent.  Under  some  conditions 
it  causes  the  valves,  and  particularly  the  hot  valve,  to  stick  or  work 
less  freely.  While  this  excess  of  tar  need  not  cause  any  serious 
trouble,  most  operators  take  precautionary  measures.  Sometimes  dis- 
tillate or  paraffin  oil  is  poured  down  the  stem  of  the  hot  valve  after 
completing  the  day's  run  to  soften  the  tar.  The  tar  trouble  may  also 
be  diminished  by  tapping  a  hole  in  the  valve  bonnet  and  pouring  a  little 
lubricating  oil  into  the  valve  through  this  opening  once  a  day. 

Actual  practice  indicates  that  the  coals  from  southern  Illinois  and 
from  Indiana  containing  less  than  1^  per  cent  of  sulphur  have  not 
caused  any  sulphur  trouble  when  used  in  the  manufacture  of  water- 
gas.  One  gas  company  reports  that  the  unpurified  gas  from  these 
coals  contains  only  5  per  cent  more  sulphur  than  the  water-gas  manufac- 
tured from  coke,  using  the  same  kind  of  oil  in  both  cases.  Some 
operators  state  that  the  gas  manufactured  with  bituminous  coal  purifies 
more  easily  than  that  produced  when  using  coke  fuel.  Serious  sulphur 
trouble  has  not  been  noticed  in  any  of  the  gas  plants  visited. 

From  the  experience  of  various  operators  with  central  district 
coals,  it  seems  that  the  fear  of  an  excessive  deposit  of  carbon  in  the 
checker  bricks  resulting  from  the  use  of  coal,  is  largely  groundless. 
At  only  one  of  the  plants  visited  was  any  abnormal  deposition  of  carbon 
reported.  In  this  case  a  loose  deposit  of  carbon  in  the  shape  of  an 
inverted  cone  was  said  to  form  in  the  interstices  of  the  superheater 
checker  bricks,  the  apex  of  the  cone  being  near  the  bottom  of  the 
checker  work  and  the  base  of  the  cone  near  the  top,  where  it  extended 
to  within  a  foot  of  the  wall.  The  set  was  8  feet  6  inches  in  diameter 
and  was  operated  24  hours  a  day.  A  sample  of  the  carbon  analyzed 
carried  over  98  per  cent  combustible  matter,  showing  that  it  was 
deposited  carbon  and  not  coal  dust.  In  operating  this  machine  some 
of  the  blast  gas  was  burned  outside  the  machine  at  the  stack.  The 
operating  cycle  consisted  of  a  three-minute  blast  and  a  four-minute 
steam  run;  the  blast  pressure  was  16  inches.     The  steam  used  was 


USE    OF    BITUMINOUS    COAL  13 

40  to  45  pounds  per  minute,  and  alternate  up  and  down  runs  were 
made. 

In  those  Illinois  gas  plants  where  good  results  with  coal  are 
being  obtained  without  the  formation  of  carbon,  the  method  of  opera- 
tion is  to  employ  a  greater  blast  pressure,  a  shorter  time  of  blast,  and 
a  greater  amount  of  steam  per  minute  during  the  runs  than  is  used 
when  coke  is  the  generator  fuel.  By  using  what  appears  to  be  an 
excessive  amount  of  steam,  the  temperatures  of  the  carburetor  and 
superheater  are  reduced  to  such  an  extent  that  the  gas  produced 
in  the  subsequent  blast  can  be  burned  entirely  within  the  machine 
without  overheating  it.  With  this  practice  no  carbon  troubles  are 
experienced  in  the  superheater. 

The  fusing  point  of  the  ash  of  central-west  coal  is  lower  than 
that  from  eastern  coke;  therefore,  to  avoid  clinker,  which  is  simply 
ash  fused  or  melted  together,  it  is  necessary  to  avoid  unduly  high 
temperatures.  For  this  reason,  if  the  fuel  bed  is  not  blasted  too  long 
and  the  air  pressure  is  not  too  high,  little  clinker  trouble  need  result. 
As  will  be  noted  in  a  later  section  of  this  circular,  there  is  a  tendency 
among  operators  to  use  relatively  more  steam  with  coal  than  with 
coke,  which  practice  together  with  the  blasting  method  employed 
usually  results  in  a  clinker  which  is  more  easily  broken  up  than  the 
clinker  from  coke. 

WATER-GAS  MANUFACTURE  AT  PLANTS  USING 
BITUMINOUS  COAL  FUEL 

As  a  result  of  the  inspection  of  water-gas  plants  using  bituminous 
coal,  it  is  possible  to  discuss  the  principal  points  in  operating  practice 
which  seem  essential  to  success.  The  advantages  and  disadvantages 
of  any  particular  method  of  operation  or  the  detailed  chemical  reac- 
tions of  the  water-gas  process  will  not  be  discussed  in  this  circular. 

The  following  variables  seem  to  be  most  important : 

1.  Kind  and  size  of  fuel. 

2.  Depth  of  fuel  bed  and  its  relation  to  blast  and  steam  cycle. 

3.  Quality  and  quantity  of  oil  used. 

4.  Distribution  of  oil  in  the  carburetor. 

5.  Temperature  maintained  in  the  carburetor  and  in  the  super- 

heater. 

6.  Purging  the  machine  with  air. 

Each  of  these  variables  has  so  important  a  bearing  upon  the  operating 
results,  and  all  are  so  inter-related  that  a  change  in  one  condition  almost 
invariably  necessitates  a  change  in  others  if  the  heat  balance  in  the 


14  WATER-GAS    MANUFACTURE 

machine,  necessary  to  good  operation,  is  to  be  maintained.  It  is  not 
possible  to  predict  exactly  what  combination  of  conditions  will  be 
necessary  in  each  case.  In  the  following,  the  tendencies  of  present 
practice,  rather  than  absolute  results  obtained  when  changing  from 
coke  to  coal,  will  be  discussed. 

Kind  and  Size  of  Fuel 

The  coal  now  used  is  either  low-sulphur  coal  from  seam  No.  6 
in  southern  Illinois  or  from  seam  No.  4  in  western  Indiana.  Other 
bituminous  coals  from  the  central  ditsrict,  if  low  in  sulphur,  could 
probably  be  used  successfully.  The  smaller  plants  use  lump  coal  about 
5  inches  in  diameter.  Lumps  larger  than  these  are  broken  up  with 
a  sledge  while  the  charging  buggy  is  being  filled,  and  fine  coal  is 
removed  by  forking.  In  the  larger  plants  it  is  the  practice  to  use  egg- 
size  coal  or  lumps  between  2  and  6  inches  in  diameter,  which  is  charged 
into  the  generator  without  preliminary  breaking. 

Depth  of  Fuel  Bed  and  Its  Relation  to  Blast  and  Steam  Cycle 

The  depth  of  the  fuel  bed  maintained  in  the  generator  and  the 
blast  and  steam  pressure  carried  during  operation  are  so  closely  inter- 
related that  they  may  well  be  discussed  together.  The  effect  of  a  thin 
fuel  bed  in  reducing  the  tendency  of  the  fuel  to  mat  together  has 
already  been  discussed.  Most  operators  find  that  the  fuel  can  best  be 
maintained  at  the  desired  depth  by  coaling  the  generator  more  fre- 
quently and  with  a  smaller  weight  of  charge  than  when  using  coke. 
Several  operators  state  that  the  weight  of  the  coal  charge  should  be 
about  80  per  cent  of  the  weight  of  the  coke  charge,  and  that  one  or 
two  fewer  runs  should  elapse  between  charging  times. 

A  decreased  depth  of  fuel  bed  permits  the  passage  of  more  air 
or  steam  through  the  fire  in  a  given  time  at  a  given  pressure.  Since 
the  amount  of  air  required  to  bring  the  fuel  bed  to  the  proper  con- 
dition varies  roughly  with  the  amount  of  fuel,  a  shallow  fire  requires 
less  blast  than  a  deep  fire.  With  bituminous  coal  most  operators  not 
only  blast  at  about  2  to  3  inches  water  pressure  less  than  when  using 
coke,  but  also  decrease  the  length  of  the  blasting  period. 

With  a  shallower  bed  of  incandescent  fuel  for  the  steam  to  act 
upon,  it  might  be  expected  that  the  duration  of  the  steam  run  and  the 
amount  of  steam  used  per  minute  should  be  decreased  in  order  to 
maintain  the  heat  balance  in  the  set.  However,  in  the  majority  of 
plants  visited  the  steam  was  not  decreased  in  the  same  proportion  as 
was  the  air  blast,  and  the  length  of  run  was  usually  the  same  as  with 


USE    OF    BITUMINOUS    COAL  15 

coke.  A  very  common  cycle  was  a  2-minute  blast  followed  by  a 
4-minute  steam  run.  A  3-minute  blast  followed  by  a  5-minute  run 
was  also  frequently  observed. 

In  the  matter  of  proportioning  the  "up"  and  "down"  runs  there 
was  a  great  difference  of  opinion.  Some  operators  alternated  the  up 
and  down  runs  after  the  set  had  been  brought  to  normal  running  con- 
ditions. Others  made  more  down  runs  than  up  runs,  while  still  others 
favored  more  up  runs.  A  few  preferred  to  "split"  every  run  as  here- 
tofore discussed.  It  was  quite  common  practice  in  the  plants  inspected 
to  use  about  10  pounds  more  of  steam  per  minute  on  the  down  runs 
than  on  the  up  runs. 

The  operating  conditions  observed  suggest  that  much  benefit  can 
be  derived  from  the  study  of  the  composition  of  the  generator  gases 
produced  under  various  conditions  of  operation  and  the  determina- 
tion of  the  amount  of  steam  passing  through  the  fire  undecomposed. 

The  conditions  actually  maintained  in  some  plants  were  impos- 
sible to  ascertain.  The  poor  condition  or  lack  of  steam  and  air  gauges 
and  meters  in  several  cases  made  experimental  work  with  a  view  to 
bettering  operating  conditions  almost  impossible.  In  a  few  cases,  care- 
lessness or  ignorance  of  those  actually  handling  the  machine  was  the 
principal  handicap  to  good  results. 

Quality  and  Quantity  of  Oil  Used 

The  quality  of  oil  used  in  a  given  plant  will  of  course  affecl 
the  operation  and  have  a  pari  in  determining  the  proper  cycle.  The 
concensus  of  opinion  seems  to  be  that  oils  from  different  fields  require 
different  heat  treatment,  and  so  it  is  impossible  to  prescribe  operating 
conditions  without  taking  the  kind  of  oil  into  account.  I  lowcvcr, 
assuming  that  a  change  is  made  from  coke  to  coal  fuel,  there  are  cer- 
tain differences  to  be  observed  in  operation. 

The  so-called  "blue  gas"  produced  from  bituminous  coal  fuel  is 
higher  in  heating  value  than  the  "blue  gas"  from  coke  since  it  con- 
tains a  considerable  percentage  of  hydrocarbons.  Consequently  less 
oil  is  required  per  1,000  cubic  feet  of  gas  to  enrich  to  the  required 
standard.  The  reduction  in  the  amount  of  oil  required  may  be  as  much 
as  0.5  gallon  per  thousand  cubic  feet  of  gas  made.  Since  the  amount 
of  gas  made  per  run  is  usually  less  with  coal  than  with  coke,  the 
amount  of  oil  required  per  run  is  of  course  less.  To  fix  the  oil  the 
same  temperatures  are  usually  maintained  in  the  carburetor  and  super- 
heater as  when  using  coke  fuel.  These  temperatures  range  from 
1250°  F.  to  1350°F. 


16  WATER-GAS    MANUFACTURE 

Distribution  of  Oil  in  the  Carburetor 

In  changing  to  coal  fuel,  the  oil  spray  in  the  carburetor  is  often 
left  as  it  was  when  coke  was  used.  The  result  is  that  with  a  decreas- 
ing oil  requirement  per  run,  it  is  necessary  to  reduce  the  rate  of  oil 
flow  through  the  nozzle  and  frequently  this  reduction  results  in  poor 
distribution.  Instead  of  spraying,  uniformly  over  the  surface  of  the 
bricks  in  the  top  of  the  carburetor,  much  of  the  oil  may  pass  down 
through  the  center  of  the  carburetor,  resulting  in  incomplete  vapori- 
zation and  low  oil  efficiency.  As  a  consequence  a  large  portion  of  the 
oil  is  wasted.  Furthermore  the  concentration  of  oil  in  the  center  of  the 
carburetor  may  cause  the  formation  of  an  excessive  deposit  of  carbon 
which  fouls  the  checker  bricks  and  soon  necessitates  recheckering. 
This  matter  should  have  the  immediate  attention  of  any  operator  mak- 
ing the  change. 

Purging  the  Machine  with  Air 

In  some  plants  it  is  the  practice  to  purge  the  machine  with  air 
after  completing  the  steam  run  and  before  raising  the  stack  valve. 
There  is  evidently  a  gain  by  doing  this,  although  oftentimes  it  is  car- 
ried so  far  that  the  dilution  of  the  gas  by  the  lean-air  gas  thus  manu- 
factured makes  necessary  the  use  of  an  excessive  amount  of  oil  to 
bring  the  gas  to  the  required  B.  t.  u.  standard.  By  watching  the  quality 
of  the  gas  the  operator  can  estimate  how  far  he  can  carry  this  purging 
process.  One  advantage  in  purging  not  usually  considered  is  that 
during  this  purging  carbon  is  being  burned  in  the  generator,  thus  caus- 
ing a  rise  of  temperature  in  the  fuel  bed;  and  at  the  same  time  the 
carburetor  and  superheater  are  being  heated  less  than  during  the  regular 
blast  period  when  blast  gas  is  being  burned  in  these  chambers.  Since 
the  usual  tendency  in  operation  is  to  allow  the  superheater  to  become 
too  hot,  this  process  of  purging  may  give  the  operator  greater  control 
over  the  temperature.  As  a  precautionary  measure,  before  opening 
the  air  blast  to  purge,  the  operator  should  make  sure  that  the  blower 
is  up  to  speed,  so  that  there  will  be  sufficient  pressure  in  the  air  lines 
to  prevent  back  firing  in  the  blast  line. 

OPERATING  DATA  FROM  TYPICAL  PLANTS  WHERE  COAL 
IS  USED  AS  GENERATOR  FUEL 

At  several  plants  where  both  water-gas  and  coal-gas  are  manu- 
factured they  are  not  metered  separately.  In  these  cases  it  is  usual 
to  estimate  the  yield  of  coal-gas  from  the  amount  of  coal  carbonized 


OPERATING   DATA  17 

and  to  estimate  the  amount  of  water-gas  as  the  difference  between 
the  combined  yield  and  the  estimated  coal-gas  yield.  Operating  data 
from  these  plants  can  not  be  used  for  accurate  comparison. 

It  was  possible,  however,  to  obtain  data  from  several  plants  where 
water-gas  only  was  manufactured  and  at  others  where  the  water-gas 
was  metered  separately.  It  should  be  remembered  that  results  obtained 
at  any  particular  plant  depend  not  only  on  the  operating  methods,  but 
on  the  quality  and  kind  of  fuel  and  oil  and  on  the  general  equipment 
and  its  physical  condition. 

As  bituminous  coals  from  only  a  few  mines  in  the  central  district 
have  been  used  in  water-gas  manufacture,  no  comparison  of  different 
coals  is  possible  at  this  time.  Also  since  the  use  of  bituminous  coal 
is  new,  the  operating  conditions  have  not  been  fully  standardized,  and 
each  operator  is  using  individual  operating  methods. 

Although  the  data  furnished  by  the  operators  was  given  as  average 
practice,  yet  the  desire  to  report  the  best  results  should  be  taken  into 
consideration.  At  some  plants  the  facilities  for  weighing  the  fuel 
were  poor  and  therefore  the  figures  given  for  fuel  consumption  may 
be  approximate  only.  The  operating  data  selected  from  four  typical 
plants  are  given  in  the  table  following : 


18 


WATER-GAS    MANUFACTURE 


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ECONOMICAL    ADVANTAGES  19 

Discussion  of  Table 

At  plant  A  it  was  possible  to  secure  figures  covering  operating 
data  when  coke  as  well  as  coal  had  been  used  as  a  fuel.  Thus  that 
part  of  the  table  under  A  gives  a  direct  comparison  at  the  same  plant 
between  coke  and  southern  Illinois  lump  coal.  At  this  plant  more 
steam  is  required  per  thousand  cubic  feet  of  gas  manufactured  with 
coal  as  fuel  than  with  coke.  Less  air  is  used  with  coal  than  with  coke 
fuel.  The  capacity  per  hour  of  the  machine  is  approximately  20  per 
cent  less  with  coal.  Moreover,  with  coal  the  generator  fuel  per  1,000 
cubic  feet  of  gas  is  increased  11.8  pounds,  or  about  27  per  cent,  but 
the  oil  used  is  decreased  0.41  gallon  per  1,000  cubic  feet  of  gas  manu- 
factured, or  11.5  per  cent. 

At  plant  B,  decidedly  less  steam  and  somewhat  more  air  are  used 
per  1,000  cubic  feet  of  gas  made  than  at  plant  A,  operating  with  coal 
fuel.  Although  the  generator  fuel  and  oil  used  per  unit  of  gas  is  some- 
what less  in  plant  B  than  in  plant  A,  yet  the  larger  size  of  the  generating 
set  at  plant  B  and  lower  quality  of  gas  made  would  account  for  these 
results.     In  general  the  results  for  plants  A  and  B  are  in  agreement. 

At  plant  C,  when  starting  a  fresh  fire  in  the  generator  each  morn- 
ing, the  first  charge  is  coke,  although  all  succeeding  charges  are  coal. 
With  this  difference  taken  into  consideration,  the  amount  of  fuel  used 
at  plant  C  checks  closely  with  that  used  at  plants  A  and  B. 

At  plant  C  it  was  found  necessary  to  burn  an  appreciable  amount 
of  the  combustible  blast  gas  at  the  stack  while  the  generator  was  being 
heated  to  the  required  temperature,  in  order  to  prevent  the  carburetor 
and  superheater  from  becoming  too  hot. 

In  general,  as  compared  with  plants  A  and  B,  less  blast  pressure 
and  shorter  steam  runs  were  used  at  plant  C,  but  the  steam  consump- 
tion per  unit  of  gas  made  was  about  the  same,  while  the  oil.  used  per 
unit  of  gas  made  was  considerably  greater. 

This  was  the  only  plant  visited  where  the  blast  gases  were  partly 
burned  at  the  stack  instead  of  being  entirely  consumed  in  the  machine. 
Another  exceptional  feature  was  that  carbon  was  deposited  in  the 
superheater  to  such  a  degree  that  the  checker  brickwork  had  to  be  laid 
in  flues  instead  of  in  the  usual  staggered  fashion.  It  is  possible  that 
the  grade  or  composition  of  the  oil  influenced  the  formation  of  the 
carbon  deposit. 

xA.t  plant  D,  on  starting  the  generator  in  the  morning,  an  extra 
number  of  down  runs  are  made,  and  hard  carbon-free  clinker  forms 
on  the  grate.  Jt  is  considered  there  that  better  results  are  obtained 
when    running  the  generator  with   this   bed   of    clinkers.      It   requires 


20  WATER-GAS    MANUFACTURE 

three  men  two  hours  each  day  to  clinker  the  machine.  The  results 
obtained  at  plant  D  agree  very  closely  with  those  obtained  at  the  other 
plants. 

In  spite  of  the  considerable  variation  in  operating-  methods  in  the 
four  plants,  a  study  of  the  results  reported  shows  that  there  is  fairly 
close  agreement.  Different  local  conditions  demand  different  treat- 
ment and  it  is  not  possible  to  say  that  any  particular  set  of  operating 
conditions  is  best  for  all  cases.  This  is  apparent  when  it  is  considered 
that  differences  in  oils,  coals,  and  gas-quality  standards,  together  with 
differences  in  operating  equipment,  make  it  necessary  for  each  oper- 
ator to  select  methods  fitting  his  own  particular  requirements. 

THE  ECONOMICAL  ADVANTAGE  OF  CENTRAL  DISTRICT 
COAL  AS  WATER-GAS  GENERATOR  FUEL 

Many  water-gas  plants  in  Illinois  and  neighboring  states  are  now 
operating  successfully  with  central  district  bituminous  coals  as  gen- 
erator fuel  in  place  of  coke.  The  use  of  coal  was  first  resorted  to 
because  of  the  shortage  of  coke.  Probably  little  or  no  profit  from 
its  use  was  anticipated.  Many  plants,  however,  are  now  realizing  a 
substantial  saving  in  the  cost  of  gas  manufacture  with  coal  fuel,  and 
other  plants  operating  under  favorable  conditions  would  doubtless  find 
its  use  profitable. 

To  determine  what  if  any  saving  can  be  realized  in  a  given  case, 
local  conditions  must  be  considered,  and  certain  assumptions  based 
upon  the  results  which  have  been  obtained  by  others  must  be  made. 
It  is  the  purpose  of  this  paper  to  apply  the  average  operating  results 
reported  by  several  plants  to  a  case  in  which  certain  fuel,  labor,  and 
operating  costs  are  assumed  and  to  point  out  how  the  various  conditions 
affect  the. cost  of  manufacture.  The  costs  assumed  do  not  represent 
the  conditions  existing  in  any  particular  plant,  but  are  taken  merely 
for  illustration.  It  is  believed  that  any  operator  can  use  his  own  figures 
and  arrive  at  a  conclusion  as  to  whether  the  use  of  coal  would  pay 
in  his  own  case. 

In  changing  from  coke  to  coal,  several  factors  are  to  be  considered 
in  determining  the  effect  of  the  change  on  the  final  cost  of  manufacture. 
These  factors  include  for  each  fuel  the  following  items : 

1.  Cost    of    the    amounts   of    materials    required   to    produce 

a  given  volume  (say  1,000  cubic  feet)  of  gas  of  the  re- 
quired quality. 

2.  Cost  of  operating  labor  per  1,000  cubic  feet  of  gas. 

3.  Cost  of  repairs  per  1,000  cubic  feet  of  gas. 


ECONOMICAL   ADVANTAGES  2l 

4.  Overhead  and  miscellaneous  expense. 

5.  Income  realized  from  the  sale  of  residuals. 

It  is  very  difficult  except  after  long  operating  experience  with  each 
fuel,  to  assign  definite  values  to  all  of  these  items,  and  in  some  cases 
the  difference  would  be  so  slight  as  to  have  little  weight  in  the  com- 
parison. In  assuming  values  for  the  different  items,  the  unit  costs 
selected  do  not  apply  to  the  operating  conditions  in  any  particular 
plant.  The  amounts  of  materials  used  per  1,000  cubic  feet  of  gas, 
however,  are  fairly  representative  of  the  present  practice  in  several 
plants. 

Cost  of  Materials 

In  the  following  comparison,  it  is  assumed  that  central  district 
bituminous  coal  can  be  delivered  at  the  gas  plant  for  $4.00  per  ton  and 
that  coke  costs  $9.00  per  ton.  In  a  mixed  gas  plant  the  unit  price 
adopted  for  coke  as  generator  fuel  may  be  somewhat  lower  than  the 
price  at  which  the  coke  could  be  bought.  In  this  comparison,  however, 
it  is  assumed  that  the  water-gas  plant  operates  as  an  independent  unit. 
From  results  obtained  by  several  plants,  35  pounds  of  coke  or  45 
pounds  of  coal  seem  to  be  typical  figures  for  generator  fuel  per  1,000 
cubic  feet  of  gas.  The  generator  fuel  cost  on  this  basis  would  be 
$0.15  per  M  for  coke  and  $0.09  per  M  for  coal. 

Most  operators  are  able  to  effect  a  substantial  saving  in  gas  oil 
when  using  coal.  For  making  a  575  B.  t.  u.  gas,  typical  amounts  are 
3.25  gallons  of  oil  with  coke  fuel  and  2.90  gallons  with  coal  fuel  per 
1,000  cubic  feet  of  gas.  At  7  cents  per  gallon  for  oil  in  each  case,  this 
gives  $0,227  with  coke  and  $0,203  with  coal. 

The  cost  of  steam  in  each  case  is  more  difficult  to  estimate.  Both 
fuel  and  labor  enter  into  this  item,  and  the  percentage  capacity  at  which 
the  steam  equipment  is  operating  in  each  case  will  largely  determine 
the  total  cost.  It  is  assumed  here  that  the  cost  per  1,000  cubic  feet 
of  gas  is  proportional  to  the  time  of  operating.  Most  operators  can 
produce  in  a  given  time  about  70  per  cent  as  much  gas  with  coal 
as  with  coke.  If  therefore  $0.05  is  assumed  as  the  cost  of  steam  with 
coke  fuel,  the  cost  when  using  coal  will  be  $0,071. 

Several  miscellaneous  materials  beside  those  mentioned,  such  as 
waste,  lubricating  oils,  electric  current  or  gas  for  lighting,  cooling 
water,  paints,  purifying  material,  etc.,  enter  into  the  manufacturing  cost. 
Of  these  none  except  the  purifying  material  cost  would  probably  be 
enough  changed  to  affect  the  comparison.  The  amount  of  sulphur  to 
be  removed  from  the  gas  in  either  case  depends  largely  upon  the  amount 
which  was  present  in  the  fuel,  if  the  same  oil  is  used  in  both  cases. 


22  WATER-GAS    MANUFACTURE 

The  cost  of  purification  with  coke  fuel  would  probably  not  exceed 
$0,008  per  1,000  cubic  feet  of  gas.  An  assumed  increase  of  10  per 
cent,  which  is  larger  than  some  operators  report,  would  give  about 
$0,009  for  coal  fuel.  In  this  case  on  account  of  the  smallness  of  the 
item,  both  labor  and  material  are  included. 

Cost  of  Operating  Labor 

The  increase  in  operating  labor  due  to  a  decrease  in  capacity 
of  about  30  per  cent  will  depend  greatly  upon  the  percentage  capacity 
at  which  the  water-gas  machinery  was  operating  with  coke  fuel.  If, 
for  example,  a  plant  is  normally  operating  8  hours  per  day  with  coke 
and  the  operating  force  is  on  a  12-hour  basis,  a  change  to  coal  will 
perhaps  permit  the  force  to  be  more  fully  employed  with  little  or  no 
increase  in  cost.  On  the  other  hand,  if  the  plant  is  already  working 
a  full  shift,  a  change  to  coal  would  necessitate  putting  on  another 
shift,  working  overtime,  or  starting  an  additional  generating  set.  For 
the  purpose  of  this  paper  it  is  assumed  that  the  operating  labor  cost 
is  proportional  to  the  time  of  operating.  If  the  generator-house  labor, 
including  the  cost  of  bringing  fuel  from  stock  pile  to  generator  is  taken 
as  $0,012  with  coke,  then  with  coal  $0,017  per  1,000  feet  of  gas  would 
seem  reasonable,  since  about  28.6  per  cent  more  coal  would  be  handled, 
and  the  apparatus  would  be  operated  about  40  per  cent  longer  to  make 
the  required  amount  of  gas.  The  miscellaneous  operating  labor  and 
works  superintendence  would  also  increase  somewhat  perhaps,  but  it 
is  not  believed  that  these  two  items,  especially  the  latter,  would  actually 
increase  in  proportion  to  the  increase  of  operating  time.  They  will 
not  be  considered  in  this  estimate. 

Cost  of  Repairs 

The  experiences  of  operators  with  coal  fuel  do  not  indicate  that 
the  wear  and  tear  on  the  apparatus  is  any  more  severe  with  coal  than 
with  coke.  While  the  apparatus  is  working  more  hours  per  day,  the 
usual  opinion  expressed  is  that  there  is  less  trouble  from  the  formation 
of  hard  clinkers  and  that  the  wear  on  the  generator  lining  caused  by 
breaking  off  the  clinkers  is  less.  It  will  be  assumed  in  this  estimate 
that  the  cost  of  repairs  per  1,000  cubic  feet  of  gas  made  is  the  same 
for  both  fuels. 

Overhead  and  Miscellaneous  Expense 

No  reason  is  apparent  why  these  expenses  should  be  materially 
affected  by  the  kind  of  generator  fuel  used,  and  they  will  not  therefore 
be  considered. 


CONCLUSIONS  23 

Income  from  Sale  of  Residuals 

The  only  residuals  obtained  from  water-gas  manufacture  are  tar, 
and,  in  the  case  of  some  of  the  larger  plants,  a  certain  amount  of  light 
oils.  The  effect  of  coal  as  generator  fuel  upon  light-oil  production 
has  not  been  studied.  As  to  tar  production  there  is  some  difference 
of  opinion.  It  is  difficult  to  measure  the  production  of  water-gas  tar 
except  where  it  has  accumulated  over  a  considerable  period  of  time. 
Some  operators  estimate  that  the  production  of  tar  increases  50  per 
cent  when  coal  is  used  as  generator  fuel.  To  be  conservative,  half  this 
increase  is  assumed  here.  The  yields  taken  are  0.5  gallon  of  tar  with 
coke  fuel  and  0.62  gallon  with  coal.  A  price  of  1.5  cents  per  gallon 
is  assumed  which  would  give  a  gross  income  of  $0,007  with  coke  and 
$0,009  with  coal. 

Summary 

Using  the  values  assumed  in  the  foregoing,  the  following  com- 
parisons may  be  tabulated : 

Table  2. — A  comparison  of  the  approximate  manufacturing  costs  of  water-gas 
with  coke  and  with  coal  as  the  generator  fuel 

Coke   fuel  Coal   fuel 

Cost  per  M  cu.  Cost  per  M  cu. 

ft.  of  gas  made  ft.  of  gas  made 

Generator  fuel    $0,150  $0,090 

Oil    227  .203 

Steam   (fuel  and  labor,  etc.) .050  .071 

Gas-making  labor    (including  fuel   handling)....             .012  .017 

Purification  expense   .008  .009 

Total    $0,447  $0,390 

Credit  from  sale  of  tar .007  .009 

Net   $0,440  $0,381 

Saving  by  the  use  of  coal  as  generator  fuel,  $0,059  per  M  cu.  ft.  of  gas  made. 

This  table  does  not  take  into  account  all  of  the  elements  of  cost 
but  only  those  which  would  seem  to  be  affected  by  the  kind  of  gen- 
erator fuel  used,  it  being  assumed  that  the  same  amount  of  gas  is  pro- 
duced pay  day  in  each  case.  Therefore  these  figures  are  not  presented 
to  show  the  actual  cost  of  gas  to  the  holder  but  merely  to  indicate 
the  approximate  saving  in  manufacturing  cost  which  might  be  effected 
under  the  conditions  assumed.  The  actual  saving  will  vary.  Some 
plants  report  considerably  higher  savings  while  others  are  not  doing 
so  well. 


24  WATER-GAS    MANUFACTURE 

CONCLUSIONS 

Inspection  of  these  plants  leads  to  the  following  conclusions  re- 
garding the  use  of  central  district  coal  as  compared  with  coke  for 
generator  fuel : 

1.  Central  district  coals  are  successfully  used  in  the  manufacture 
of  water  gas. 

2.  Under  present  operating  conditions  a  decrease  in  producing 
capacity  of  from  20  to  35  per  cent  may  be  anticipated  from  the  use 
of  coal  as  compared  with  good  coke. 

3.  Clinker  troubles  are  not  usually  as  serious  as  with  coke  fuel. 

4.  There  are  no  serious  sulphur  troubles  if  selected  low-sulphur 
coals  are  used. 

5.  Gas  made  with  central  district  coal  as  generator  fuel  costs  less 
per  1,000  cubic  feet  under  present  conditions  than  does  gas  with  coke 
generator  fuel.  Though  more  fuel  is  used  per  1,000  cubic  feet  of  gas, 
this  is  offset  by  the  lower  price  of  the  fuel,  the  decrease  in  the  amount 
of  oil  required,  and  the  increase  in  amount  of  tar  for  sale. 

SUGGESTED  PROBLEMS  FOR  FURTHER  STUDY 

As  a  result  of  this  preliminary  work,  a  number  of  problems  in  the 
manufacture  of  water-gas  have  been  suggested  for  experimental  study 
as  follows : 

Determining  the  best  operating  cycle  under  the  varying  conditions. 

Increasing  the  capacity  of  the  water-gas  machine. 

Reducing  the  required  amount  of  generator  fuel  and  of  oil. 

Eliminating  the  smoke  trouble. 

Reducing  the  quantity  of  carbon  in  the  ash  and  clinker. 

Results  obtainable  with  various  kinds  and  sizes  of  central  district 
coal. 

The  gas  section  of  the  Cooperative  Mining  Investigations  is  en- 
gaged in  experimental  work  on  certain  of  these  problems  and  hopes 
to  distribute  further  reports  and  recommendations. 


PUBLICATIONS  OF 
ILLINOIS  MINING  INVESTIGATIONS 


ILLINOIS  STATE  GEOLOGICAL  SURVEY  DIVISION 
URBANA,  ILLINOIS 

Bulletin     1.     Preliminary  report  on  organization  and  method  of  investigations,   1913. 

Bulletin     3.     Chemical  study  of  Illinois  coals,  by  S.  W.  Parr,  1916. 

Bulletin  10.     Coal  resources  of  District  I  (Longwall),  by  G.  H.  Cady,  1915. 

Bulletin  11.     Coal  resources  of  District  VII,  by  Fred  H.  Kay,  1915. 

Bulletin  14.     Coal  resources  of  District  VIII  (Danville),  by  Fred  H.  Kay  and  K.  D.  White, 

1915. 
Bulletin   15.     Coal  resources  of  District  VI,  by  G.  H.  Cady,  1916. 
Bulletin  16.     Coal  resources  of  District  II  (Jackson  Co.),  by  G.  H.  Cady,  1917. 
Bulletin  17.     Surface  subsidence  in  Illinois  resulting  from  coal  mining,  by  Lewis  E.  Young, 

1916. 
Bulletin  18.     Tests  on  clay  materials  available  in  Illinois  coal  mines,  by  R.  T.  Stull  and  R.  K. 

Hursh,  1917. 
Bulletin  20.     Carbonization  of  Illinois  coals  in  inclined  gas  retorts,  by  F.  K.  Ovitz,  1918. 
Bulletin  21.     The  manufacture  of  retort  coal-gas  in  the  central  states,  using  low-sulphur  coal 

from  Illinois,  Indiana,  and  western  Kentucky,  by   W.  A.  Dunkley,  and   W . 

W.  Odell,  1918. 
Bulletin  22.     Water-gas  manufacture  with  central  district  bituminous  coals  as  generator  fuel, 

by  W.  W.  Odell  and  W.  A.  Dunkley,  1918. 


Bulletin 

2. 

Bulletin 

4. 

Bulletin 

5. 

Bulletin 

6. 

Bulletin 

7. 

Bulletin 

8. 

Bulletin 

9. 

Bulletin 

12. 

Bulletin 

13. 

Bulletin  91. 

Bulletin 

100. 

ENGINEERING  EXPERIMENT  STATION 
URBANA,  ILLINOIS 
Coal  mining  practice  in  District  VIII   (Danville),  by  S.  O.  Andros,  1913. 
Coal  mining  practice  in  District  VII,  by  S.  O.  Andros,  1914. 
Coal  mining  practice  in  District  I  (Longwall),  by  S.  O.  Andros,  1914. 
Coal  mining  practice  in  District  V,  by  S.  O.  Andros,  1914. 
Coal  mining  practice  in  District  II,  by  S.  O.  Andros,  1914. 
Coal  mining  practice  in  District  VI,  by  S.  O.  Andros,  1914. 
Coal  mining  practice  in  District  III,  by  S.  O.  Andros,  1915. 
Coal  mining  practice  in  District  IV,  by  S.  O.  Andros,  1915. 
Coal  mining  in  Illinois,  by  S.  O.  Andros,   1915.     (Complete  resum6  of  all  the 

district   reports.) 
Subsidence  resulting  from  mining,  by  L.  E.  Young  and  H.  H.  Stoek,  1916. 
Percentage  of  extraction   of  bituminous  coal  with  special  reference  to   Illinois 

conditions,  by  C.  M.  Young,  1917. 


U.  S.  BUREAU  OF  MINES 
WASHINGTON,  D.  C. 

Bulletin     72.     Occurrence  of  explosive  gases  in  coal  mines,  by  N.  H.  Darton,  1915. 

Bulletin     83.     The  humidity  of  mine  air,  by  R.  Y.  Williams,  1914. 

Bulletin     99.     Mine  ventilation  stoppings,  by  R.  Y.  Williams,  1915. 

Bulletin  102.  The  inflammability  of  Illinois  coal  dusts,  by  J.  K.  Clement  and  L.  A.  Scholl, 
Jr.,  1916. 

Bulletin  137.  Use  of  permissible  explosives  in  the  coal  mines  of  Illinois,  by  J.  R.  Fleming 
and  J.  W.  Koster,   1917. 

Bulletin   138.     Coking  of  Illinois  coals,  by  F.  K.  Ovitz,  1917. 

Technical  Paper  190.  Methane  accumulations  from  interrupted  ventilation,  with  special  ref- 
erence to  coal  mines  in  Illinois  and  Indiana,  by  H.  I.  Smith  and  Robert  J. 
Hamon,  1918. 


